Component control in semiconductor performance processing with stable product offsets

ABSTRACT

A method of making a semiconductor device includes collecting process control parameters during operation of a processing tool processing a product. The method further includes calculating a processing tool offset for the processing tool based on the collected process control parameters and calculating a product offset based on the collected process control parameters. The method further includes determining whether the product offset is stable and calculating an offset time for processing the product using the processing tool based on the calculated processing tool offset if the product offset is stable.

BACKGROUND

Due to imperfections and process variations, machinery used tomanufacture semiconductor devices have offset times with respect tocalculated processing times. A calculated processing time is atheoretical time for completing a processing step assuming idealconditions. An offset time is a variation between the calculatedprocessing time and an actual time for completing the processing step.In some approaches, the offset time is determined by processing a groupof test wafers and analyzing the test wafers to determine whether theprocessing step was properly completed, whether the processing step wasnot properly completed or whether the test wafers were over processed.

Preventive maintenance is performed on machinery used to fabricatesemiconductor devices in order to maintain the machinery in workingorder. During preventive maintenance, a backup machine is used in placeof the machinery. An offset time of the backup machine is oftendifferent from an offset time of the machinery normally used tofabricate the semiconductor devices.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments are illustrated by way of example, and not bylimitation, in the figures of the accompanying drawings, whereinelements having the same reference numeral designations represent likeelements throughout. It is emphasized that, in accordance with standardpractice in the industry various features may not be drawn to scale andare used for illustration purposes only. In fact, the dimensions of thevarious features in the drawings may be arbitrarily increased or reducedfor clarity of discussion.

FIG. 1 is a flow chart of a method of determining an offset time inaccordance with one or more embodiments;

FIG. 2 is a graph of error versus different processing tools inaccordance with one or more embodiments;

FIG. 3 is a graph of an average processing time for different productsin a variety of processing tools in accordance with one or moreembodiments;

FIG. 4 is a graph of a processing time for a variety of products inaccordance with one or more embodiments; and

FIG. 5 is a schematic view of a control system for implementing a methodsuch as that of FIG. 1 in accordance with one or more embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are examples and are not intended to belimiting.

FIG. 1 is a flow chart of a method 100 of determining an offset time inaccordance with one or more embodiments. In operation 102, processcontrol parameters are collected during operation of a processing tool.During semiconductor device manufacturing, each process tool isconfigured to perform a specific task or set of tasks. The processcontrol parameters include a processing time the processing tool toperform the specific task or set of tasks on each type of product. Theprocess control parameters also include a type of product processed andwhether the product passed quality control tests. In some embodiments,the processing tool is used during normal operation of manufacturingsemiconductor devices. In some embodiments, the processing tool is abackup processing tool used in place of the normal processing toolduring a preventive maintenance cycle.

FIG. 2 is a graph 200 of an error versus different processing tools inaccordance with one or more embodiments. An X-axis of graph 200indicates different processing tools. A Y-axis of graph 200 is anarbitrary unit for measuring the production error. Graph 200 indicates arandom error 202 associated with minor process variations duringfabrication of the semiconductor devices. In some embodiments, randomerror 202 is unavoidable to some degree. Graph 200 also indicates anaccumulated error 204 which is a combination of random error 202 anderror introduced due to the processing tool and the product beingprocessed. When a magnitude of accumulated error 204 exceeds a thresholdvalue, the product fails quality control tests. Maintaining theaccumulated error 204 within the threshold value increases productionyield.

By collecting data on the process control parameters, e.g., in operation102, a performance of specific product/processing tool combinations areable to be determined over time by analyzing historical data. Once theperformance of the specific product/processing tool combinations isknown, an offset time for adjusting the processing time is able to bedetermined to reduce accumulated error 204 to fall within the thresholdvalue so that the products pass quality control tests. In someembodiments, the offset time is determined using statistical analysis ofhistorical data. In some instances, the historical data is obtainedusing test wafers. In some embodiments, the historical data is obtainedduring previous operation of the processing tool. However, increasedtime used for determining the offset time for specificproduct/processing tool combinations reduces a yield of thesemiconductor device fabrication process.

In at least one example, the processing tool is an etching chamber andthe specific task is etching a trench. During operation, a wafer isintroduced into the etching chamber. In some embodiments, the waferincludes additional layers over a substrate and the additional layersare subjected to an etching process. In some embodiments, the wafer doesnot include additional layers and the substrate is subjected to theetching process. Based on a material being etched, a type of etchant andother parameters, a theoretical processing time is able to becalculated. A difference exists between the theoretical processing timeand an actual etching time to properly complete etching the trench. Thisdifference is call the offset time. Due to process variations, e.g.,flow rates of materials into the etching chamber, purity of the etchant,etc., or variations within between etching chambers, the offset timebetween respective etching chambers is also different.

Whenever a new machine is introduced into a semiconductor devicefabrication process, an offset time is determined. For example, when afirst etching chamber is subject to preventive maintenance, a backupetching chamber is used while the first etching chamber is offline. Thebackup etching chamber is inserted into the production process bydirecting wafers to the backup etching chamber. In some embodiments,wafers are directed to the backup etching chamber using front openinguniversal pods (FOUPs) to carry wafers from the first etching chamber tothe backup etching chamber. In some embodiments, wafers are directed tothe backup etching chamber using FOUPs to carry wafers from a processingtool used prior to the etching process to the backup etching chamber. Insome embodiments, one backup etching chamber is used during manufactureof several different products.

The backup etching chamber has a different offset time than the firstetching chamber. In some approaches, each time the backup etchingchamber is used a group of test wafers for a specific product areprocessed using the backup etching chamber. The group of test wafers isthen analyzed to determine the offset time for the backup etchingchamber for each type of product. In at least one example, a linearrelationship is applicable to determine the offset time. In someembodiments, the linear relationship for an etching process isrepresented by Formula 1:Etched Amount=a*Target Depth+Offset(time,tool,product)  (1)where the Etched Amount is an actual amount of material removed by theetching process, a is an etch rate of the etchant on the productmaterial, Target Depth is the desired trench depth, and Offset is theoffset time. The Offset is a function of the processing time, theprocessing tool and the product being processed.

Returning to FIG. 1, in operation 104, an average of the process controlparameters of each process tool and each product is calculated. Byaveraging the process control parameters, an impact of extraneousprocessing variables, e.g., substrate or layer defect, on the processcontrol parameters is reduced.

FIG. 3 is a graph 300 of an average processing time for differentproducts for a variety of processing tools in accordance with one ormore embodiments. An X-axis of graph 300 indicates different products. AY-axis of graph 300 indicates an average processing time. Differentprocessing tools are indicated based on the legend in graph 300. Usingthe example of an etching process, each tool Tool #1-Tool #6 indicates adifferent etching chamber and each product Product #1-Product #7indicates a different semiconductor device. As indicated by graph 300,the processing time for each product/processing tool combination varies.

Using Tool #3 as an example, assuming a theoretical processing time of35 seconds, the average offset time with respect to the product #1/tool#3 combination to product #5/tool #3 combination is a positive value,indicating an increased processing time, with respect to the theoreticalprocessing time, is used to reach the desired trench depth. The averageoffset time with respect to the product #6/tool #3 combination isnegative, indicating a decreased processing time, with respect to thetheoretical processing time, is used to reach the desired trench depth.Graph 300 indicates the average processing time of the product #7/tool#3 combination is nearly equal to the theoretical processing timemeaning the offset time is nearly zero.

Returning to FIG. 1, in operation 106 a processing tool offset and aproduct offset are calculated. Using the average processing time for theproduct/processing tool combinations, a portion of the offset which isattributable to each of the product and the processing tool in eachproduct/processing tool combination is able to be determined. Byseparating the offset based on the contribution from the product and thecontribution from the processing tool Formula 1 is modified as seen inFormula 2:Etched Amount=a*Target Depth+Tool Offset(time)+Product Offset(time)  (2)where Tool Offset is a portion of the offset contributed by theprocessing tool, which is a function of processing time, and the ProductOffset is a portion of the offset contributed by the product, which isalso a function of processing time. Separating the offset into theprocessing tool offset and the product offset enables identification ofa source of the offset for the product/processing tool combination.

FIG. 4 is a graph 400 of a processing time for a variety of products inaccordance with one or more embodiments. An X-axis of graph 400indicates different processes performed on the product. A Y-axis ofgraph 300 indicates an offset of the process. Plots having circularshaped data points indicate different individual products. A plot havingrectangular shaped data points indicates an average of the offset forthe products. Graph 400 indicates that each product experiences asimilar offset during each process. Therefore, the portion of the offsetthat is contributed by the products in graph 400 is able to beconsidered independent of processing time. By considering the productcontributed offset to be independent of processing time, Formula 2 ismodified as seen in Formula 3:Etched Amount=a*Target Depth+Tool Offset(time)+Product Offset  (3)where the Product Offset is a portion of the offset contributed by theproduct, which is independent of processing time. By determining thatproduct offset is independent of processing time, the determination ofthe total offset time focuses on the offset contributed only by theprocessing tool.

If the test wafers approach from above is applied to an examplesemiconductor device fabrication process which includes 36 differentproducts and 10 different processing tools, 360 different groups of testwafers would be used to determine the offset time for eachproduct/processing tool combination. Each group of test wafers takes,e.g., approximately 1 day to process and analyze. As a result,determining the offset time for all product/processing tool combinationstakes approximately 360 days.

In contrast, using method 100 reduces a number of groups of test wafersto 10 if the product offset is determined to be independent ofprocessing time. The decreased time used for test wafer processing andanalysis increases the yield and overall production of the semiconductordevice fabrication process.

Returning to FIG. 1, in operation 108 the product offset is analyzed todetermine whether the product offset is stable. In some embodiments, theproduct offset is considered stable if the product offset is independentof processing time. In some embodiments, the product offset isconsidered stable if a variation of the product offset for differentproducts is within a pre-determined tolerance. In some embodiments, thevariation is calculated using a magnitude of a difference between agreatest product offset and a smallest product offset. In someembodiments, the variation is calculated using statistical analysis suchas standard deviation, average, or other suitable calculations. In someembodiments, if an amount of historical data available for calculatingthe product offset is below a threshold value, the data is consideredinsufficiently reliable the product offset is considered not to bestable.

If the product offset is determined to be stable, method 100 continueswith operation 110 in which the offset time for a product/processingtool combination is determined based on the processing tool offset. Theoffset time of the product/processing tool combination does not accountfor offset contributed by the product. In some embodiments, theprocessing tool offset is determined based on analysis of historicaldata for the specific processing tool. In some embodiments, thehistorical data analysis includes a regression analysis, a histogramanalysis or other suitable statistical analysis of previous usage of theprocessing tool.

If the product offset is determined not to be stable, method 100continues with operation 112, in which the offset time is determined byprocessing at least one test wafer. The offset time includes bothprocessing tool offset and product offset which are both a function ofprocessing time. In some embodiments, a group of test wafers areprocessed and analyzed to determine the offset time.

FIG. 5 is a schematic view of a control system 500 for implementing themethod of FIG. 1 in accordance with one or more embodiments. Controlsystem 500 includes a hardware processor 502 and a non-transitory,computer readable storage medium 504 encoded with, i.e., storing, thecomputer program code 506, i.e., a set of executable instructions.Computer readable storage medium 504 is also encoded with instructions507 for interfacing with manufacturing machines for producing the memoryarray. The processor 502 is electrically coupled to the computerreadable storage medium 504 via a bus 508. The processor 502 is alsoelectrically coupled to an I/O interface 510 by bus 508. A networkinterface 512 is also electrically connected to the processor 502 viabus 508. Network interface 512 is connected to a network 514, so thatprocessor 502 and computer readable storage medium 504 are capable ofconnecting to external elements via network 514. The processor 502 isconfigured to execute the computer program code 506 encoded in thecomputer readable storage medium 504 in order to cause system 500 to beusable for performing a portion or all of the operations as described inmethod 100.

In some embodiments, the processor 502 is a central processing unit(CPU), a multi-processor, a distributed processing system, anapplication specific integrated circuit (ASIC), and/or a suitableprocessing unit.

In some embodiments, the computer readable storage medium 504 is anelectronic, magnetic, optical, electromagnetic, infrared, and/or asemiconductor system (or apparatus or device). For example, the computerreadable storage medium 504 includes a semiconductor or solid-statememory, a magnetic tape, a removable computer diskette, a random accessmemory (RAM), a read-only memory (ROM), a rigid magnetic disk, and/or anoptical disk. In some embodiments using optical disks, the computerreadable storage medium 504 includes a compact disk-read only memory(CD-ROM), a compact disk-read/write (CD-R/W), and/or a digital videodisc (DVD).

In some embodiments, the storage medium 504 stores the computer programcode 506 configured to cause system 500 to perform method 100. In someembodiments, the storage medium 504 also stores information needed forperforming a method 100 as well as information generated duringperforming the method 100, such as a processing tool offset parameter516, a product offset parameter 518, an offset time parameter 520, aprocessing tool parameter 522, a product parameter 524 and/or a set ofexecutable instructions to perform the operation of method 100.

In some embodiments, the storage medium 504 stores instructions 507 forinterfacing with manufacturing machines. The instructions 507 enableprocessor 502 to generate manufacturing instructions readable by themanufacturing machines to effectively implement method 100 during amanufacturing process.

Control system 500 includes I/O interface 510. I/O interface 510 iscoupled to external circuitry. In some embodiments, I/O interface 510includes a keyboard, keypad, mouse, trackball, trackpad, and/or cursordirection keys for communicating information and commands to processor502.

Control system 500 also includes network interface 512 coupled to theprocessor 502. Network interface 512 allows system 500 to communicatewith network 514, to which one or more other computer systems areconnected. Network interface 512 includes wireless network interfacessuch as BLUETOOTH, WIFI, WIMAX, GPRS, or WCDMA; or wired networkinterface such as ETHERNET, USB, or IEEE-1394. In some embodiments,method 100 is implemented in two or more systems 500, and informationsuch as processing tool offset, product offset, offset time, processingtool and product are exchanged between different systems 500 via network514.

System 500 is configured to receive information related to a processingtool offset time through I/O interface 510. The information istransferred to processor 502 via bus 508 to determine a processing tooloffset. The processing tool offset is then stored in computer readablemedium 504 as processing tool parameter 516. Control system 500 isconfigured to receive information related to product offset time throughI/O interface 510. The information is stored in computer readable medium504 as product offset parameter 518. Control system 500 is configured toreceive information related to offset time through I/O interface 510.The information is stored in computer readable medium 504 as offset timeparameter 520. Control system 500 is configured to receive informationrelated to processing tool used through I/O interface 510. Theinformation is stored in computer readable medium 504 as processing toolparameter 522. Control system 500 is configured to receive informationrelated to a product being produced through I/O interface 510. Theinformation is stored in computer readable medium 504 as productparameter 524. In some embodiments, the information related to at leastone of offset time, processing tool used and product being produced areextracted from memory array layout parameter 518 by processor 502 andstored as the appropriate parameter in computer code 506.

During operation, processor 502 executes a set of instructions todetermine a product offset time based on product offset parameter 516.For method 100, if the product offset time is stable, processor 502determines the offset time for storing in offset time parameter 520based on processing tool offset parameter 516. If the product timeoffset time is not stable, processor 502 provides instructions throughI/O interface 510 or network interface 512 to process and analyze agroup of test wafers.

One aspect of this description relates to a method of making asemiconductor device. The method includes collecting process controlparameters during operation of a processing tool processing a product.The method further includes calculating a processing tool offset for theprocessing tool based on the collected process control parameters andcalculating a product offset based on the collected process controlparameters. The method further includes determining whether the productoffset is stable and calculating an offset time for processing theproduct using the process tool based on the calculated processing tooloffset if the product offset is stable.

Another aspect of this description relates to a method of making asemiconductor device. The method includes removing a first processingtool from a production line and inserting a second processing tool intothe production line. The method further includes determining an offsettime for processing a product using the second processing tool.Determining the offset time of the second processing tool includescollecting process control parameters during operation of the secondprocessing tool. Determining the offset time further includescalculating a processing tool offset of the second processing tool basedon the collected process control parameters and calculating a productoffset based on the collected process control parameters. Determiningthe offset time further includes determining whether the product offsetis stable and calculating the offset time based on the calculatedprocessing tool offset if the product offset is stable.

Still another aspect of this description relates to a control system.The control system includes a processing tool, a processor connected tothe processing tool, and a non-transitory computer readable mediumconnected to the processor. The non-transitory computer readable mediumincluding instructions for collecting process control parameters duringoperation of a processing tool processing a product. The non-transitorycomputer readable medium further includes instructions for calculating aprocessing tool offset based on the collected process control parametersand calculating a product offset based on the collected process controlparameters. The non-transitory computer readable medium further includesinstructions for determining whether the product offset is stable andcalculating an offset time for processing the product using theprocessing tool, using the processor, based on the calculated processingtool offset if the product offset is stable.

It will be readily seen by one of ordinary skill in the art that thedisclosed embodiments fulfill one or more of the advantages set forthabove. After reading the foregoing specification, one of ordinary skillwill be able to affect various changes, substitutions of equivalents andvarious other embodiments as broadly disclosed herein. It is thereforeintended that the protection granted hereon be limited only by thedefinition contained in the appended claims and equivalents thereof.

What is claimed is:
 1. A method of making a semiconductor devicecomprising: collecting one or more process control parameters duringoperation of a processing tool processing a product; calculating aprocessing tool offset for the processing tool based on the collectedprocess control parameters, wherein the processing tool offset is afirst portion of a process offset time attributable to a processingtool; calculating a product offset based on the collected processcontrol parameters, wherein the product tool offset is a second portionof the process offset time attributable to a product; determiningwhether the product offset is stable, wherein the determining whetherthe product offset is stable is based on a difference between aprocessing time for different products being within a pre-determinedtolerance and a number of processed wafers exceeding a threshold amount;calculating an offset time for processing the product using theprocessing tool based on the calculated processing tool offset, withoutconsidering the product offset, if the product offset is stable; andmanufacturing the semiconductor device using the processing tool basedon the calculated offset time.
 2. The method of claim 1, furthercomprising calculating the offset time for processing the product usingthe processing tool based on the calculated processing tool offset andthe calculated product offset if the product offset is not stable. 3.The method of claim 1, further comprising averaging the process controlparameters for each processing tool and each product.
 4. The method ofclaim 3, wherein calculating the processing tool offset is performedusing the averaged process control parameters.
 5. The method of claim 3,wherein calculating the product offset is performed using the averagedprocess control parameters.
 6. The method of claim 1, wherein thedetermining whether the product offset is stable comprises: performing astatistical analysis of the product offset based on historical data; anddetermining the product offset to be stable if a difference between theprocessing time for the different products is within the pre-determinedtolerance.
 7. The method of claim 1, wherein the determining whether theproduct offset is stable comprises: determining whether the number ofprocessed wafers exceeds the threshold value; and determining theproduct offset to not be stable if the number does not exceed thethreshold amount.
 8. A method of making a semiconductor devicecomprising: removing a first processing tool from a production line;inserting a second processing tool into the production line; anddetermining an offset time for processing a product using the secondprocessing tool, wherein determining the offset time of the secondprocessing tool comprises: collecting one or more process controlparameters during operation of the second processing tool; calculating aprocessing tool offset of the second processing tool based on thecollected process control parameters, wherein the processing tool offsetis a first portion of a process offset time attributable to a processingtool; calculating a product offset based on the collected processcontrol parameters, wherein the product tool offset is a second portionof the process offset time attributable to a product; determiningwhether the product offset is stable, wherein the determining whetherthe product offset is stable is based on a difference between aprocessing time for different products being within a pre-determinedtolerance and a number of processed wafers exceeding a threshold amount;and calculating the offset time based on the calculated processing tooloffset, without considering the product offset, if the product offset isstable; and manufacturing the semiconductor device using the secondprocessing tool based on the calculated offset time.
 9. The method ofclaim 8, wherein collecting process control parameters is performedprior to inserting the second processing tool into the production line.10. The method of claim 8, wherein determining the offset time of thesecond processing tool further comprises calculating the offset timebased on the calculated processing tool offset and the calculatedproduct offset if the product offset is not stable.
 11. The method ofclaim 8, wherein determining the offset time of the second processingtool further comprises averaging the process control parameters for eachprocessing tool and each product.
 12. The method of claim 11, whereincalculating the processing tool offset is performed using the averagedprocess control parameters.
 13. The method of claim 11, whereincalculating the product offset is performed using the averaged processcontrol parameters.
 14. The method of claim 8, wherein determiningwhether the product offset is stable comprises: performing a statisticalanalysis of the product offset based on historical data for the secondprocessing tool; and determining the product offset to be stable if adifference between a processing time for different products is within apre-determined tolerance.
 15. The method of claim 8, wherein determiningwhether the product offset is stable comprises: determining whether anumber of wafers processed by the second processing tool exceeds athreshold value; and determining the product offset to not be stable ifthe number does not exceed the threshold amount.
 16. A control systemcomprising: a processing tool; a processor connected to the processingtool; and a non-transitory computer readable medium connected to theprocessor, the non-transitory computer readable medium includinginstructions for: collecting process control parameters during operationof a processing tool processing a product, wherein the process controlparameters are based on a combination of the processing tool and aproduct; calculating a processing tool offset based on the collectedprocess control parameters, wherein the processing tool offset is afirst portion of a process offset time attributable to a processingtool; calculating a product offset, of the product, based on thecollected process control parameters, wherein the product offset is asecond portion of the process offset time attributable to a product;determining whether the product offset is stable, wherein thedetermining whether the product offset is stable is based on adifference between a processing time for different products being withina pre-determined tolerance and a number of processed wafers exceeding athreshold amount; and calculating, using the processor, an offset timefor processing the product by the processing tool based on thecalculated processing tool offset, without considering the productoffset, in response to a determination that the product offset isstable, wherein the processing tool is configured to manufacture asemiconductor device based on the calculated offset time.
 17. Thecontrol system of claim 16, wherein the non-transitory computer readablemedium further includes instructions for calculating the offset time forprocessing the product using the processing tool, using the processor,based on the calculated processing tool offset and the calculatedproduct offset if the product offset is not stable.
 18. The controlsystem of claim 16, wherein the non-transitory computer readable mediumfurther includes instructions for: averaging the process controlparameters for each processing tool and each product; calculating theprocessing tool offset using the averaged process control parameters;and calculating the product offset using the averaged process controlparameters.
 19. The control system of claim 16, wherein thenon-transitory computer readable medium further includes instructionsfor: performing a statistical analysis of the product offset based onhistorical data for the processing tool; and determining the productoffset to be stable if a difference between a processing time fordifferent products is within a pre-determined tolerance.
 20. The controlsystem of claim 16, wherein the non-transitory computer readable mediumfurther includes instructions for: determining whether a number ofwafers processed by the processing tool exceeds a threshold value; anddetermining the product offset to not be stable if the number does notexceed the threshold amount.